Ottawa police are once again asking the public for help in an ongoing sexual assault investigation that links at least three sexual assaults over 14 months to one suspect.

Last month, police revealed there were seven other cases that might be linked to the same suspect and on Thursday, they re-issued the surveillance video of the suspect in a sexual assault on Draper Avenue as part of those seven cases.

Ottawa police re-issued two previously released sketches of a suspect they believe is linked to three sexual assaults over 14 months. (Ottawa police)

Ottawa police Sgt. Richard Dugal said the assault, which happened in the Greenbank Towers apartment building in March 2013, could be linked to the others.

Police have received 350 tips so far since their appeal last month and have talked to about 120 people, Dugal added.

The victims in the three linked cases were attacked between August 2012 and October 2013 and they were between 18 and 30 years old. All had been walking alone before they were attacked and they were choked on Banner Road, Lancaster Road and Aldea Avenue, police said.

Aug. 5, 2012, at about 3 a.m.: A woman was sexually assaulted at her home on Banner Road.

June 26, 2013, at about 10 p.m.: A woman was sexually assaulted on a footpath between Lancaster Road and Erinbrook Crescent.

Oct. 7, 2013, at about 9:50 p.m.: A woman was sexually assaulted on Aldea Avenue near Lasalle Street.

Police sources said the cases are linked with DNA evidence, and fingerprints were also gathered at the scenes of the Banner Road and Greenbank Road attacks.

Police have also shared two composite sketches and they are asking the public for any information on the suspect.

The suspect is described as possibly being of Middle Eastern descent with short dark hair. He spoke English during the attacks and possibly a foreign language. He's in his 20s, standing five feet nine inches tall to five feet eleven inches tall (175 to 180 cm) with a slim to medium build. He had trimmed facial hair, thick eyebrows and a prominent nose.

Potential witness was in nearby store

Ottawa police released this photo on Feb. 13, 2014 saying he was a witness to a sexual assault in the Chapman Mills neighbourhood. They would like to talk to him about what he saw. (Photo courtesy of Ottawa police)

Dugal also said police are looking for a possible witness they said likely saw or heard something during a Jan. 5 attack in Barrhaven's Chapman Mills neighbourhood, another of the seven attacks similar to the DNA-linked attacks.

He said surveillance video shows a man in a nearby store at the Strandherd Crossing complex, about ten minutes away from where a woman was pulled to a secluded area and assaulted while walking home around 10 p.m.

Staff later confirmed to CBC News the surveillance video came from the Metro grocery store.

This potential witness is described as a white man with dark facial hair, wearing a dark puffy jacket with zippers, a tuque and light-coloured pants.

Police aren't confirming if the attacker in this incident is linked to the three definitively linked attacks.

Anyone who thinks they know this potential witness or the suspect is asked to call the Ottawa police's tip line at 613-236-1222, ext. 4774 or Crime Stoppers at 613-233-8477.